As music fans, arts-and-crafts enthusiasts and general hippies poured into Manchester, Tenn. for Day 1 of the 2013 Bonnaroo festival on Thursday (June 13), the names "McCartney," "Mumford" and "Petty" drew interest as this year's coming attractions. But the kickoff day of the annual collection of sprawling fields and soaring alternative sounds is always utilized to showcase niche artists while allowing their audiences to get accustomed to the formidable festival grounds in front of them. With no main stage acts performing, artists like HAIM, Purity Ring and Alt-J drew enormous crowds and gained new supporters who had previously been craning their necks to see what the fuss was about.

Of course, Day 1 of Bonnaroo 2013 wasn't just about the many solid live performances, crazy outfits or even makeshift instruments for sale -- instead, the talk of Thursday was Saturday night's headliner canceling its highly anticipated set.

1. After Mumford & Sonsannounced on Thursday afternoon that they would be canceling their Bonnaroo appearance, a big hole opened up in the festival's Saturday night headlining slot. Simultaneous requests were quickly made to Jack Johnson and Darius Rucker, Billboard has learned. Johnson was already on the grounds for surprise press appearances in support of his upcoming album "From Here To Now To You," while Rucker has a previously announced concert in Balitmore on Saturday night that would need to be re-scheduled. Festival founders Superfly and PR firm Big Hassle were expected to make the final announcement by early afternoon on Friday.

2. Midway through HAIM's razor-sharp early evening set, bassist Este Haim squinted over to the left side of the crowd and called out something unusual: a little boy in the front row, large yellow muffs covering his fragile ears, his tiny fingers gripping onto a sign that read "KISS ME ESTE." The bassist, of course, obliged, first running off the stage to deliver a smooch on the cheek, then hugging the child tightly, then seizing him into her arms, and finally bringing him back up on stage to help out with a performance of "Send Me Down." The little boy, whose name was Isa and whose age couldn't have been more than 5, received some hearty applause upon returning to the crowd.

3. British electro-folk act Alt-J swung by the Billboard press tent after dusk to talk their current tour of the U.S. and the challenge of playing 60-minute sets at festivals in support of a 44-minute album. Luckily, the band has been busy making new music for films lately, contributing the new song "Buffalo" to last year's "Silver Linings Playbook" and recently completing a score for the Toby Jones-starring film "Leave To Remain." The band's Gwil Sainsbury was mum on details of the latter project, only to say it'll sound similar to Alt-J's debut "An Awesome Wave" in the sense that the songs "are all bound together by Joe [Newman]'s voice."

4. As the only major rapper on Thursday's bill, veteran Atlanta MC Killer Mike brought an aura of realness and Dirty South credibility to Bonnaroo for his after-midnight set. The "R.A.P. Music" auteur hyped his upcoming "Run The Jewels" album with El-P, provoked an impromptu debate about the NSA, and got the masses to rail against Ronald Reagan with a middle finger in the air. He also tipped his cap to his past, shouting out Outkast and leading a funky rendition of his verse from their classic "The Whole World." There was a rant against hype men (because his is "his own voice"), and in closing, a profound statement: "If Jesus came today where the hell you think he'd be? Getting high at Bonnaroo with me."

5. Weather-related flight delays prevented Brooklyn indie rockers DIIV from making their Friday afternoon set. However, pneumonia forced Earl Sweatshirt to cancel his Friday afternoon set, giving DIIV a chance to play Bonnaroo after all, now at 4:00 PM in The Other Tent.

6. Purity Ring's live performances are a trippy spectacle, best exemplified by the fluorescent lanterns that decorate the stage and double as percussion pieces for producer Corin Roddick. Their set time came just after sundown, creating the perfect setting for a selection of cuts from their 2012 debut "Shrines." With Roddick providing the backbone of slithery indie-meets-rap beats, singer Megan James crooned the band's magical, often macabre lyrics. The best responses came to "Belispeak" and "Fineshrine," although there was also an ingenious cover of Soulja Boy's "Grammy."

7. As always, the arts-and-crafts portion of Bonnaroo, dubbed the "Centeroo Market," was a fascinating pastiche of various goods and services, often with a bizarre musical slant. Want to buy a guitar made out of a cigar box? Have the desire to build a drum, in a station succinctly titled "Build A Drum"? Or perhaps you're looking for a new tote bag, with two old Talking Heads vinyl covers serving as the sides? It's all available in the wonderfully weird market in the heart of Bonnaroo.

8. Ohio electro-pop duo twenty one pilots played their first Bonnaroo with an acrobatic mid-afternoon set, and talked to Billboard about how they scored the opening slot on Fall Out Boy's upcoming fall tour with Panic! At The Disco. "I basically kept tweeting Pete [Wentz] until he listened," said singer Tyler Joseph.

9. In one of the day's earliest sets in the tents, hip-hop producer AraabMuzik brought the feel of an EDM fest to Bonnaroo with a pummeling DJ set beneath the Other Stage dome. In the midday heat, Araab (real name: Abraham Orellana) somehow kept his cool as the only man in the audience rocking a hoodie.

10. The two biggest stages of Bonnaroo, the What Stage and the Which Stage, are never open on Thursday at the festival, but at 1:30 AM, the Which Stage crew was busy testing out the light show in anticipation for the next three days' worth of performance. Although there was no music playing during the lighting test, a group of two dozen (potentially drug-addled) festival goers was standing next to the stage, gazing at the wordless technicolor blasts as most music fans turned in for the evening. Perhaps they were just confused and thought they were watching Pretty Lights?